summaryrefslogtreecommitdiffstats
path: root/src/gui/image/qjpeghandler.cpp
blob: 481101db93791f647efb475ce72c5d094435f966 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
/****************************************************************************
**
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the plugins of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL21$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Digia gives you certain additional
** rights. These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qjpeghandler_p.h"

#include <qimage.h>
#include <qvariant.h>
#include <qvector.h>
#include <qbuffer.h>
#include <qmath.h>
#include <private/qsimd_p.h>

#include <stdio.h>      // jpeglib needs this to be pre-included
#include <setjmp.h>

#ifdef FAR
#undef FAR
#endif

// including jpeglib.h seems to be a little messy
extern "C" {
// mingw includes rpcndr.h but does not define boolean
#if defined(Q_OS_WIN) && defined(Q_CC_GNU)
#   if defined(__RPCNDR_H__) && !defined(boolean)
        typedef unsigned char boolean;
#       define HAVE_BOOLEAN
#   endif
#endif

#define XMD_H           // shut JPEGlib up
#if defined(Q_OS_UNIXWARE)
#  define HAVE_BOOLEAN  // libjpeg under Unixware seems to need this
#endif
#include <jpeglib.h>
#ifdef const
#  undef const          // remove crazy C hackery in jconfig.h
#endif
}

QT_BEGIN_NAMESPACE

void QT_FASTCALL convert_rgb888_to_rgb32_C(quint32 *dst, const uchar *src, int len)
{
    // Expand 24->32 bpp.
    for (int i = 0; i < len; ++i) {
        *dst++ = qRgb(src[0], src[1], src[2]);
        src += 3;
    }
}

typedef void (QT_FASTCALL *Rgb888ToRgb32Converter)(quint32 *dst, const uchar *src, int len);

static Rgb888ToRgb32Converter rgb888ToRgb32ConverterPtr = convert_rgb888_to_rgb32_C;

struct my_error_mgr : public jpeg_error_mgr {
    jmp_buf setjmp_buffer;
};

#if defined(Q_C_CALLBACKS)
extern "C" {
#endif

static void my_error_exit (j_common_ptr cinfo)
{
    my_error_mgr* myerr = (my_error_mgr*) cinfo->err;
    char buffer[JMSG_LENGTH_MAX];
    (*cinfo->err->format_message)(cinfo, buffer);
    qWarning("%s", buffer);
    longjmp(myerr->setjmp_buffer, 1);
}

static void my_output_message(j_common_ptr cinfo)
{
    char buffer[JMSG_LENGTH_MAX];
    (*cinfo->err->format_message)(cinfo, buffer);
    qWarning("%s", buffer);
}

#if defined(Q_C_CALLBACKS)
}
#endif


static const int max_buf = 4096;

struct my_jpeg_source_mgr : public jpeg_source_mgr {
    // Nothing dynamic - cannot rely on destruction over longjump
    QIODevice *device;
    JOCTET buffer[max_buf];
    const QBuffer *memDevice;

public:
    my_jpeg_source_mgr(QIODevice *device);
};

#if defined(Q_C_CALLBACKS)
extern "C" {
#endif

static void qt_init_source(j_decompress_ptr)
{
}

static boolean qt_fill_input_buffer(j_decompress_ptr cinfo)
{
    my_jpeg_source_mgr* src = (my_jpeg_source_mgr*)cinfo->src;
    qint64 num_read = 0;
    if (src->memDevice) {
        src->next_input_byte = (const JOCTET *)(src->memDevice->data().constData() + src->memDevice->pos());
        num_read = src->memDevice->data().size() - src->memDevice->pos();
        src->device->seek(src->memDevice->data().size());
    } else {
        src->next_input_byte = src->buffer;
        num_read = src->device->read((char*)src->buffer, max_buf);
    }
    if (num_read <= 0) {
        // Insert a fake EOI marker - as per jpeglib recommendation
        src->next_input_byte = src->buffer;
        src->buffer[0] = (JOCTET) 0xFF;
        src->buffer[1] = (JOCTET) JPEG_EOI;
        src->bytes_in_buffer = 2;
    } else {
        src->bytes_in_buffer = num_read;
    }
    return TRUE;
}

static void qt_skip_input_data(j_decompress_ptr cinfo, long num_bytes)
{
    my_jpeg_source_mgr* src = (my_jpeg_source_mgr*)cinfo->src;

    // `dumb' implementation from jpeglib

    /* Just a dumb implementation for now.  Could use fseek() except
     * it doesn't work on pipes.  Not clear that being smart is worth
     * any trouble anyway --- large skips are infrequent.
     */
    if (num_bytes > 0) {
        while (num_bytes > (long) src->bytes_in_buffer) {  // Should not happen in case of memDevice
            num_bytes -= (long) src->bytes_in_buffer;
            (void) qt_fill_input_buffer(cinfo);
            /* note we assume that qt_fill_input_buffer will never return false,
            * so suspension need not be handled.
            */
        }
        src->next_input_byte += (size_t) num_bytes;
        src->bytes_in_buffer -= (size_t) num_bytes;
    }
}

static void qt_term_source(j_decompress_ptr cinfo)
{
    my_jpeg_source_mgr* src = (my_jpeg_source_mgr*)cinfo->src;
    if (!src->device->isSequential())
        src->device->seek(src->device->pos() - src->bytes_in_buffer);
}

#if defined(Q_C_CALLBACKS)
}
#endif

inline my_jpeg_source_mgr::my_jpeg_source_mgr(QIODevice *device)
{
    jpeg_source_mgr::init_source = qt_init_source;
    jpeg_source_mgr::fill_input_buffer = qt_fill_input_buffer;
    jpeg_source_mgr::skip_input_data = qt_skip_input_data;
    jpeg_source_mgr::resync_to_restart = jpeg_resync_to_restart;
    jpeg_source_mgr::term_source = qt_term_source;
    this->device = device;
    memDevice = qobject_cast<QBuffer *>(device);
    bytes_in_buffer = 0;
    next_input_byte = buffer;
}


inline static bool read_jpeg_size(int &w, int &h, j_decompress_ptr cinfo)
{
    (void) jpeg_calc_output_dimensions(cinfo);

    w = cinfo->output_width;
    h = cinfo->output_height;
    return true;
}

#define HIGH_QUALITY_THRESHOLD 50

inline static bool read_jpeg_format(QImage::Format &format, j_decompress_ptr cinfo)
{

    bool result = true;
    switch (cinfo->output_components) {
    case 1:
        format = QImage::Format_Indexed8;
        break;
    case 3:
    case 4:
        format = QImage::Format_RGB32;
        break;
    default:
        result = false;
        break;
    }
    cinfo->output_scanline = cinfo->output_height;
    return result;
}

static bool ensureValidImage(QImage *dest, struct jpeg_decompress_struct *info,
                             const QSize& size)
{
    QImage::Format format;
    switch (info->output_components) {
    case 1:
        format = QImage::Format_Indexed8;
        break;
    case 3:
    case 4:
        format = QImage::Format_RGB32;
        break;
    default:
        return false; // unsupported format
    }

    if (dest->size() != size || dest->format() != format) {
        *dest = QImage(size, format);

        if (format == QImage::Format_Indexed8) {
            dest->setColorCount(256);
            for (int i = 0; i < 256; i++)
                dest->setColor(i, qRgb(i,i,i));
        }
    }

    return !dest->isNull();
}

static bool read_jpeg_image(QImage *outImage,
                            QSize scaledSize, QRect scaledClipRect,
                            QRect clipRect, volatile int inQuality, j_decompress_ptr info, struct my_error_mgr* err  )
{
    if (!setjmp(err->setjmp_buffer)) {
        // -1 means default quality.
        int quality = inQuality;
        if (quality < 0)
            quality = 75;

        // If possible, merge the scaledClipRect into either scaledSize
        // or clipRect to avoid doing a separate scaled clipping pass.
        // Best results are achieved by clipping before scaling, not after.
        if (!scaledClipRect.isEmpty()) {
            if (scaledSize.isEmpty() && clipRect.isEmpty()) {
                // No clipping or scaling before final clip.
                clipRect = scaledClipRect;
                scaledClipRect = QRect();
            } else if (scaledSize.isEmpty()) {
                // Clipping, but no scaling: combine the clip regions.
                scaledClipRect.translate(clipRect.topLeft());
                clipRect = scaledClipRect.intersected(clipRect);
                scaledClipRect = QRect();
            } else if (clipRect.isEmpty()) {
                // No clipping, but scaling: if we can map back to an
                // integer pixel boundary, then clip before scaling.
                if ((info->image_width % scaledSize.width()) == 0 &&
                        (info->image_height % scaledSize.height()) == 0) {
                    int x = scaledClipRect.x() * info->image_width /
                            scaledSize.width();
                    int y = scaledClipRect.y() * info->image_height /
                            scaledSize.height();
                    int width = (scaledClipRect.right() + 1) *
                                info->image_width / scaledSize.width() - x;
                    int height = (scaledClipRect.bottom() + 1) *
                                 info->image_height / scaledSize.height() - y;
                    clipRect = QRect(x, y, width, height);
                    scaledSize = scaledClipRect.size();
                    scaledClipRect = QRect();
                }
            } else {
                // Clipping and scaling: too difficult to figure out,
                // and not a likely use case, so do it the long way.
            }
        }

        // Determine the scale factor to pass to libjpeg for quick downscaling.
        if (!scaledSize.isEmpty() && info->image_width && info->image_height) {
            if (clipRect.isEmpty()) {
                double f = qMin(double(info->image_width) / scaledSize.width(),
                                double(info->image_height) / scaledSize.height());

                // libjpeg supports M/8 scaling with M=[1,16]. All downscaling factors
                // are a speed improvement, but upscaling during decode is slower.
                info->scale_num   = qBound(1, qCeil(8/f), 8);
                info->scale_denom = 8;
            } else {
                info->scale_denom = qMin(clipRect.width() / scaledSize.width(),
                                         clipRect.height() / scaledSize.height());

                // Only scale by powers of two when clipping so we can
                // keep the exact pixel boundaries
                if (info->scale_denom < 2)
                    info->scale_denom = 1;
                else if (info->scale_denom < 4)
                    info->scale_denom = 2;
                else if (info->scale_denom < 8)
                    info->scale_denom = 4;
                else
                    info->scale_denom = 8;
                info->scale_num = 1;

                // Correct the scale factor so that we clip accurately.
                // It is recommended that the clip rectangle be aligned
                // on an 8-pixel boundary for best performance.
                while (info->scale_denom > 1 &&
                       ((clipRect.x() % info->scale_denom) != 0 ||
                        (clipRect.y() % info->scale_denom) != 0 ||
                        (clipRect.width() % info->scale_denom) != 0 ||
                        (clipRect.height() % info->scale_denom) != 0)) {
                    info->scale_denom /= 2;
                }
            }
        }

        // If high quality not required, use fast decompression
        if( quality < HIGH_QUALITY_THRESHOLD ) {
            info->dct_method = JDCT_IFAST;
            info->do_fancy_upsampling = FALSE;
        }

        (void) jpeg_calc_output_dimensions(info);

        // Determine the clip region to extract.
        QRect imageRect(0, 0, info->output_width, info->output_height);
        QRect clip;
        if (clipRect.isEmpty()) {
            clip = imageRect;
        } else if (info->scale_denom == info->scale_num) {
            clip = clipRect.intersected(imageRect);
        } else {
            // The scale factor was corrected above to ensure that
            // we don't miss pixels when we scale the clip rectangle.
            clip = QRect(clipRect.x() / int(info->scale_denom),
                         clipRect.y() / int(info->scale_denom),
                         clipRect.width() / int(info->scale_denom),
                         clipRect.height() / int(info->scale_denom));
            clip = clip.intersected(imageRect);
        }

        // Allocate memory for the clipped QImage.
        if (!ensureValidImage(outImage, info, clip.size()))
            longjmp(err->setjmp_buffer, 1);

        // Avoid memcpy() overhead if grayscale with no clipping.
        bool quickGray = (info->output_components == 1 &&
                          clip == imageRect);
        if (!quickGray) {
            // Ask the jpeg library to allocate a temporary row.
            // The library will automatically delete it for us later.
            // The libjpeg docs say we should do this before calling
            // jpeg_start_decompress().  We can't use "new" here
            // because we are inside the setjmp() block and an error
            // in the jpeg input stream would cause a memory leak.
            JSAMPARRAY rows = (info->mem->alloc_sarray)
                              ((j_common_ptr)info, JPOOL_IMAGE,
                               info->output_width * info->output_components, 1);

            (void) jpeg_start_decompress(info);

            while (info->output_scanline < info->output_height) {
                int y = int(info->output_scanline) - clip.y();
                if (y >= clip.height())
                    break;      // We've read the entire clip region, so abort.

                (void) jpeg_read_scanlines(info, rows, 1);

                if (y < 0)
                    continue;   // Haven't reached the starting line yet.

                if (info->output_components == 3) {
                    uchar *in = rows[0] + clip.x() * 3;
                    QRgb *out = (QRgb*)outImage->scanLine(y);
                    rgb888ToRgb32ConverterPtr(out, in, clip.width());
                } else if (info->out_color_space == JCS_CMYK) {
                    // Convert CMYK->RGB.
                    uchar *in = rows[0] + clip.x() * 4;
                    QRgb *out = (QRgb*)outImage->scanLine(y);
                    for (int i = 0; i < clip.width(); ++i) {
                        int k = in[3];
                        *out++ = qRgb(k * in[0] / 255, k * in[1] / 255,
                                      k * in[2] / 255);
                        in += 4;
                    }
                } else if (info->output_components == 1) {
                    // Grayscale.
                    memcpy(outImage->scanLine(y),
                           rows[0] + clip.x(), clip.width());
                }
            }
        } else {
            // Load unclipped grayscale data directly into the QImage.
            (void) jpeg_start_decompress(info);
            while (info->output_scanline < info->output_height) {
                uchar *row = outImage->scanLine(info->output_scanline);
                (void) jpeg_read_scanlines(info, &row, 1);
            }
        }

        if (info->output_scanline == info->output_height)
            (void) jpeg_finish_decompress(info);

        if (info->density_unit == 1) {
            outImage->setDotsPerMeterX(int(100. * info->X_density / 2.54));
            outImage->setDotsPerMeterY(int(100. * info->Y_density / 2.54));
        } else if (info->density_unit == 2) {
            outImage->setDotsPerMeterX(int(100. * info->X_density));
            outImage->setDotsPerMeterY(int(100. * info->Y_density));
        }

        if (scaledSize.isValid() && scaledSize != clip.size()) {
            *outImage = outImage->scaled(scaledSize, Qt::IgnoreAspectRatio, quality >= HIGH_QUALITY_THRESHOLD ? Qt::SmoothTransformation : Qt::FastTransformation);
        }

        if (!scaledClipRect.isEmpty())
            *outImage = outImage->copy(scaledClipRect);
        return !outImage->isNull();
    }
    else
        return false;
}

struct my_jpeg_destination_mgr : public jpeg_destination_mgr {
    // Nothing dynamic - cannot rely on destruction over longjump
    QIODevice *device;
    JOCTET buffer[max_buf];

public:
    my_jpeg_destination_mgr(QIODevice *);
};


#if defined(Q_C_CALLBACKS)
extern "C" {
#endif

static void qt_init_destination(j_compress_ptr)
{
}

static boolean qt_empty_output_buffer(j_compress_ptr cinfo)
{
    my_jpeg_destination_mgr* dest = (my_jpeg_destination_mgr*)cinfo->dest;

    int written = dest->device->write((char*)dest->buffer, max_buf);
    if (written == -1)
        (*cinfo->err->error_exit)((j_common_ptr)cinfo);

    dest->next_output_byte = dest->buffer;
    dest->free_in_buffer = max_buf;

    return TRUE;
}

static void qt_term_destination(j_compress_ptr cinfo)
{
    my_jpeg_destination_mgr* dest = (my_jpeg_destination_mgr*)cinfo->dest;
    qint64 n = max_buf - dest->free_in_buffer;

    qint64 written = dest->device->write((char*)dest->buffer, n);
    if (written == -1)
        (*cinfo->err->error_exit)((j_common_ptr)cinfo);
}

#if defined(Q_C_CALLBACKS)
}
#endif

inline my_jpeg_destination_mgr::my_jpeg_destination_mgr(QIODevice *device)
{
    jpeg_destination_mgr::init_destination = qt_init_destination;
    jpeg_destination_mgr::empty_output_buffer = qt_empty_output_buffer;
    jpeg_destination_mgr::term_destination = qt_term_destination;
    this->device = device;
    next_output_byte = buffer;
    free_in_buffer = max_buf;
}


static inline void set_text(const QImage &image, j_compress_ptr cinfo, const QString &description)
{
    QMap<QString, QString> text;
    foreach (const QString &key, image.textKeys()) {
        if (!key.isEmpty())
            text.insert(key, image.text(key));
    }
    foreach (const QString &pair, description.split(QLatin1String("\n\n"))) {
        int index = pair.indexOf(QLatin1Char(':'));
        if (index >= 0 && pair.indexOf(QLatin1Char(' ')) < index) {
            QString s = pair.simplified();
            if (!s.isEmpty())
                text.insert(QLatin1String("Description"), s);
        } else {
            QString key = pair.left(index);
            if (!key.simplified().isEmpty())
                text.insert(key, pair.mid(index + 2).simplified());
        }
    }
    if (text.isEmpty())
        return;

    for (QMap<QString, QString>::ConstIterator it = text.constBegin(); it != text.constEnd(); ++it) {
        QByteArray comment = it.key().toLatin1();
        if (!comment.isEmpty())
            comment += ": ";
        comment += it.value().toLatin1();
        if (comment.length() > 65530)
            comment.truncate(65530);
        jpeg_write_marker(cinfo, JPEG_COM, (JOCTET *)comment.constData(), comment.size());
    }
}

static bool write_jpeg_image(const QImage &image, QIODevice *device, volatile int sourceQuality, const QString &description)
{
    bool success = false;
    const QVector<QRgb> cmap = image.colorTable();

    struct jpeg_compress_struct cinfo;
    JSAMPROW row_pointer[1];
    row_pointer[0] = 0;

    struct my_jpeg_destination_mgr *iod_dest = new my_jpeg_destination_mgr(device);
    struct my_error_mgr jerr;

    cinfo.err = jpeg_std_error(&jerr);
    jerr.error_exit = my_error_exit;
    jerr.output_message = my_output_message;

    if (!setjmp(jerr.setjmp_buffer)) {
        // WARNING:
        // this if loop is inside a setjmp/longjmp branch
        // do not create C++ temporaries here because the destructor may never be called
        // if you allocate memory, make sure that you can free it (row_pointer[0])
        jpeg_create_compress(&cinfo);

        cinfo.dest = iod_dest;

        cinfo.image_width = image.width();
        cinfo.image_height = image.height();

        bool gray=false;
        switch (image.format()) {
        case QImage::Format_Mono:
        case QImage::Format_MonoLSB:
        case QImage::Format_Indexed8:
            gray = true;
            for (int i = image.colorCount(); gray && i--;) {
                gray = gray & (qRed(cmap[i]) == qGreen(cmap[i]) &&
                               qRed(cmap[i]) == qBlue(cmap[i]));
            }
            cinfo.input_components = gray ? 1 : 3;
            cinfo.in_color_space = gray ? JCS_GRAYSCALE : JCS_RGB;
            break;
        default:
            cinfo.input_components = 3;
            cinfo.in_color_space = JCS_RGB;
        }

        jpeg_set_defaults(&cinfo);

        qreal diffInch = qAbs(image.dotsPerMeterX()*2.54/100. - qRound(image.dotsPerMeterX()*2.54/100.))
                         + qAbs(image.dotsPerMeterY()*2.54/100. - qRound(image.dotsPerMeterY()*2.54/100.));
        qreal diffCm = (qAbs(image.dotsPerMeterX()/100. - qRound(image.dotsPerMeterX()/100.))
                        + qAbs(image.dotsPerMeterY()/100. - qRound(image.dotsPerMeterY()/100.)))*2.54;
        if (diffInch < diffCm) {
            cinfo.density_unit = 1; // dots/inch
            cinfo.X_density = qRound(image.dotsPerMeterX()*2.54/100.);
            cinfo.Y_density = qRound(image.dotsPerMeterY()*2.54/100.);
        } else {
            cinfo.density_unit = 2; // dots/cm
            cinfo.X_density = (image.dotsPerMeterX()+50) / 100;
            cinfo.Y_density = (image.dotsPerMeterY()+50) / 100;
        }


        int quality = sourceQuality >= 0 ? qMin(int(sourceQuality),100) : 75;
        jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);
        jpeg_start_compress(&cinfo, TRUE);

        set_text(image, &cinfo, description);

        row_pointer[0] = new uchar[cinfo.image_width*cinfo.input_components];
        int w = cinfo.image_width;
        while (cinfo.next_scanline < cinfo.image_height) {
            uchar *row = row_pointer[0];
            switch (image.format()) {
            case QImage::Format_Mono:
            case QImage::Format_MonoLSB:
                if (gray) {
                    const uchar* data = image.constScanLine(cinfo.next_scanline);
                    if (image.format() == QImage::Format_MonoLSB) {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (i & 7)));
                            row[i] = qRed(cmap[bit]);
                        }
                    } else {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (7 -(i & 7))));
                            row[i] = qRed(cmap[bit]);
                        }
                    }
                } else {
                    const uchar* data = image.constScanLine(cinfo.next_scanline);
                    if (image.format() == QImage::Format_MonoLSB) {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (i & 7)));
                            *row++ = qRed(cmap[bit]);
                            *row++ = qGreen(cmap[bit]);
                            *row++ = qBlue(cmap[bit]);
                        }
                    } else {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (7 -(i & 7))));
                            *row++ = qRed(cmap[bit]);
                            *row++ = qGreen(cmap[bit]);
                            *row++ = qBlue(cmap[bit]);
                        }
                    }
                }
                break;
            case QImage::Format_Indexed8:
                if (gray) {
                    const uchar* pix = image.constScanLine(cinfo.next_scanline);
                    for (int i=0; i<w; i++) {
                        *row = qRed(cmap[*pix]);
                        ++row; ++pix;
                    }
                } else {
                    const uchar* pix = image.constScanLine(cinfo.next_scanline);
                    for (int i=0; i<w; i++) {
                        *row++ = qRed(cmap[*pix]);
                        *row++ = qGreen(cmap[*pix]);
                        *row++ = qBlue(cmap[*pix]);
                        ++pix;
                    }
                }
                break;
            case QImage::Format_RGB888:
                memcpy(row, image.constScanLine(cinfo.next_scanline), w * 3);
                break;
            case QImage::Format_RGB32:
            case QImage::Format_ARGB32:
            case QImage::Format_ARGB32_Premultiplied:
                {
                    const QRgb* rgb = (const QRgb*)image.constScanLine(cinfo.next_scanline);
                    for (int i=0; i<w; i++) {
                        *row++ = qRed(*rgb);
                        *row++ = qGreen(*rgb);
                        *row++ = qBlue(*rgb);
                        ++rgb;
                    }
                }
                break;
            default:
                {
                    // (Testing shows that this way is actually faster than converting to RGB888 + memcpy)
                    QImage rowImg = image.copy(0, cinfo.next_scanline, w, 1).convertToFormat(QImage::Format_RGB32);
                    const QRgb* rgb = (const QRgb*)rowImg.constScanLine(0);
                    for (int i=0; i<w; i++) {
                        *row++ = qRed(*rgb);
                        *row++ = qGreen(*rgb);
                        *row++ = qBlue(*rgb);
                        ++rgb;
                    }
                }
                break;
            }
            jpeg_write_scanlines(&cinfo, row_pointer, 1);
        }

        jpeg_finish_compress(&cinfo);
        jpeg_destroy_compress(&cinfo);
        success = true;
    } else {
        jpeg_destroy_compress(&cinfo);
        success = false;
    }

    delete iod_dest;
    delete [] row_pointer[0];
    return success;
}

class QJpegHandlerPrivate
{
public:
    enum State {
        Ready,
        ReadHeader,
        Error
    };

    QJpegHandlerPrivate(QJpegHandler *qq)
        : quality(75), iod_src(0), state(Ready), q(qq)
    {}

    ~QJpegHandlerPrivate()
    {
        if(iod_src)
        {
            jpeg_destroy_decompress(&info);
            delete iod_src;
            iod_src = 0;
        }
    }

    bool readJpegHeader(QIODevice*);
    bool read(QImage *image);

    int quality;
    QVariant size;
    QImage::Format format;
    QSize scaledSize;
    QRect scaledClipRect;
    QRect clipRect;
    QString description;
    QStringList readTexts;

    struct jpeg_decompress_struct info;
    struct my_jpeg_source_mgr * iod_src;
    struct my_error_mgr err;

    State state;

    QJpegHandler *q;
};

/*!
    \internal
*/
bool QJpegHandlerPrivate::readJpegHeader(QIODevice *device)
{
    if(state == Ready)
    {
        state = Error;
        iod_src = new my_jpeg_source_mgr(device);

        info.err = jpeg_std_error(&err);
        err.error_exit = my_error_exit;
        err.output_message = my_output_message;

        jpeg_create_decompress(&info);
        info.src = iod_src;

        if (!setjmp(err.setjmp_buffer)) {
            jpeg_save_markers(&info, JPEG_COM, 0xFFFF);

            (void) jpeg_read_header(&info, TRUE);

            int width = 0;
            int height = 0;
            read_jpeg_size(width, height, &info);
            size = QSize(width, height);

            format = QImage::Format_Invalid;
            read_jpeg_format(format, &info);

            for (jpeg_saved_marker_ptr marker = info.marker_list; marker != NULL; marker = marker->next) {
                if (marker->marker == JPEG_COM) {
                    QString key, value;
                    QString s = QString::fromLatin1((const char *)marker->data, marker->data_length);
                    int index = s.indexOf(QLatin1String(": "));
                    if (index == -1 || s.indexOf(QLatin1Char(' ')) < index) {
                        key = QLatin1String("Description");
                        value = s;
                    } else {
                        key = s.left(index);
                        value = s.mid(index + 2);
                    }
                    if (!description.isEmpty())
                        description += QLatin1String("\n\n");
                    description += key + QLatin1String(": ") + value.simplified();
                    readTexts.append(key);
                    readTexts.append(value);
                }
            }

            state = ReadHeader;
            return true;
        }
        else
        {
            return false;
        }
    }
    else if(state == Error)
        return false;
    return true;
}

bool QJpegHandlerPrivate::read(QImage *image)
{
    if(state == Ready)
        readJpegHeader(q->device());

    if(state == ReadHeader)
    {
        bool success = read_jpeg_image(image, scaledSize, scaledClipRect, clipRect, quality, &info, &err);
        if (success) {
            for (int i = 0; i < readTexts.size()-1; i+=2)
                image->setText(readTexts.at(i), readTexts.at(i+1));

            state = Ready;
            return true;
        }

        state = Error;
    }

    return false;

}

Q_GUI_EXPORT void QT_FASTCALL qt_convert_rgb888_to_rgb32_neon(quint32 *dst, const uchar *src, int len);
Q_GUI_EXPORT void QT_FASTCALL qt_convert_rgb888_to_rgb32_ssse3(quint32 *dst, const uchar *src, int len);
extern "C" void qt_convert_rgb888_to_rgb32_mips_dspr2_asm(quint32 *dst, const uchar *src, int len);

QJpegHandler::QJpegHandler()
    : d(new QJpegHandlerPrivate(this))
{
#if defined(__ARM_NEON__)
    // from qimage_neon.cpp

    if (qCpuHasFeature(NEON))
        rgb888ToRgb32ConverterPtr = qt_convert_rgb888_to_rgb32_neon;
#endif // __ARM_NEON__
#if defined(QT_COMPILER_SUPPORTS_SSSE3)
    // from qimage_ssse3.cpp

    if (false) {
    } else if (qCpuHasFeature(SSSE3)) {
        rgb888ToRgb32ConverterPtr = qt_convert_rgb888_to_rgb32_ssse3;
    }
#endif // QT_COMPILER_SUPPORTS_SSSE3
#if defined(QT_COMPILER_SUPPORTS_MIPS_DSPR2)
    if (qCpuHasFeature(DSPR2)) {
        rgb888ToRgb32ConverterPtr = qt_convert_rgb888_to_rgb32_mips_dspr2_asm;
    }
#endif // QT_COMPILER_SUPPORTS_DSPR2
}

QJpegHandler::~QJpegHandler()
{
    delete d;
}

bool QJpegHandler::canRead() const
{
    if(d->state == QJpegHandlerPrivate::Ready && !canRead(device()))
        return false;

    if (d->state != QJpegHandlerPrivate::Error) {
        setFormat("jpeg");
        return true;
    }

    return false;
}

bool QJpegHandler::canRead(QIODevice *device)
{
    if (!device) {
        qWarning("QJpegHandler::canRead() called with no device");
        return false;
    }

    char buffer[2];
    if (device->peek(buffer, 2) != 2)
        return false;
    return uchar(buffer[0]) == 0xff && uchar(buffer[1]) == 0xd8;
}

bool QJpegHandler::read(QImage *image)
{
    if (!canRead())
        return false;
    return d->read(image);
}

bool QJpegHandler::write(const QImage &image)
{
    return write_jpeg_image(image, device(), d->quality, d->description);
}

bool QJpegHandler::supportsOption(ImageOption option) const
{
    return option == Quality
        || option == ScaledSize
        || option == ScaledClipRect
        || option == ClipRect
        || option == Description
        || option == Size
        || option == ImageFormat;
}

QVariant QJpegHandler::option(ImageOption option) const
{
    switch(option) {
    case Quality:
        return d->quality;
    case ScaledSize:
        return d->scaledSize;
    case ScaledClipRect:
        return d->scaledClipRect;
    case ClipRect:
        return d->clipRect;
    case Description:
        d->readJpegHeader(device());
        return d->description;
    case Size:
        d->readJpegHeader(device());
        return d->size;
    case ImageFormat:
        d->readJpegHeader(device());
        return d->format;
    default:
        break;
    }

    return QVariant();
}

void QJpegHandler::setOption(ImageOption option, const QVariant &value)
{
    switch(option) {
    case Quality:
        d->quality = value.toInt();
        break;
    case ScaledSize:
        d->scaledSize = value.toSize();
        break;
    case ScaledClipRect:
        d->scaledClipRect = value.toRect();
        break;
    case ClipRect:
        d->clipRect = value.toRect();
        break;
    case Description:
        d->description = value.toString();
        break;
    default:
        break;
    }
}

QByteArray QJpegHandler::name() const
{
    return "jpeg";
}

QT_END_NAMESPACE